Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Scaleshell Mussel

We, the U.S. Fish and Wildlife Service (Service), determine the scaleshell mussel (Leptodea leptodon) to be an endangered species under the Endangered Species Act of 1973, as amended (Act). The scaleshell mussel historically occurred in 55 rivers in 13 states in the eastern United States. Currently, the species is known to exist in 14 rivers (and may occur in 6 others) within the Mississippi River Basin in Missouri, Oklahoma, and Arkansas. Its abundance and distribution have decreased markedly due to habitat loss and adverse effects associated with water quality degradation, sedimentation, channelization, sand and gravel mining, dredging, and reservoir construction.